\documentclass[border=2pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{math,calc,intersections,through,angles,arrows.meta,shapes.geometric,shadows,quotes,spy,datavisualization,datavisualization.formats.functions,plotmarks}
\tikzset{every picture/.style={samples=300,smooth,line join=round,thick,>=Stealth,font=\small}}

\begin{document}

   \begin{tikzpicture}[scale=.4]
      \draw[->](-2,0)--(5.5,0)node[below]{$x$};
      \draw[->](0,-4.5)--(0,4.5)node[right]{$y$};
      \coordinate[label=-135:$O$](O)at(0,0);
      \draw[cyan,domain=-4.5:4.5]plot(\x*\x/4,\x);
      \coordinate[label=left:$C$](C)at(2,1);
      \draw[red](C)circle(2);
      \coordinate[label=above:$P$](P)at(4,4);
      \draw[cyan,domain=-4.5:4.5]plot(-1,\x);
      \draw (P)--(tangent cs:node=C,point={(P)},solution=1)--(C.center)--cycle;
  \end{tikzpicture}    
    
\end{document}